Approximately half of all motorcycles in NZ are rego exempt or rego expired right now

[old slider]

Nah. You can do what you like at home as a householder. It's not a workplace. From the Act:

20 Meaning of workplace

(1) In this Act, unless the context otherwise requires, a workplace—
(a) means a place where work is being carried out, or is customarily carried out, for a business or undertaking; and
(b) includes any place where a worker goes, or is likely to be, while at work.

(2) In this section, place includes—
(a) a vehicle, vessel, aircraft, ship, or other mobile structure; and
(b) any waters and any installation on land, on the bed of any waters, or floating on any waters.

Thanks Oakie.

[Swoop]

Cheers for the clarification Oakie!

Do you know if we need to have scaffolding certificate etc or can anyone chuck it up? in case something goes wrong and they try and blame the scaffolding installation process.

A very good mate is a roofer and quotes customers with "owner to supply scaffolding". He's been to quite a few of these OSH courses and says "so long as it is compliant" (tested and certified) and installed according to the regulations (distances from building, qty of boards, etc).
It would pay to check, once again, prior to charging in to it.